1. Field of the Invention
This invention relates to a method of increasing the molecular weight of hydroxyl endblocked polydiorganosiloxane and to the polydiorganosiloxane obtained thereby.
2. Description of the Prior Art
The hydroxyl endblocked polydiorganosiloxanes and the silanes used in the present invention are known in the art. The silanes used in this invention are described by Toporcer and Crossan in U.S. Pat. No. 3,776,933 which is hereby incorporated by reference to show the silanes and the preparation thereof.
Klebe in U.S. Pat. No. 3,488,371 describes the following silanes ##STR2## Klebe describes that these silanes can be hydrolyzed with water in a solvent to yield rubbery siloxanes.
Toporcer and Crossan in U.S. Pat. No. 3,776,933 describe silanes of the formula EQU R".sub.x Si{N(R'")C(O) R'}.sub.4-x
where R' is methyl, ethyl or phenyl, R" is a hydrocarbon radical, R'" is ethyl, propyl or phenyl and x is 1, 2 or 3, as useful as crosslinking agents in silicone rubber, as hydrolyzable silanes to make silicone resins, as chain extenders in silicone rubbers, as endblockers for silicone fluids and silylating agents.
Toporcer and Clark in U.S. Pat. No. 3,776,934 describes methylvinyldi-(N-methylacetamido) silane and teach that it is useful as an effective chain extender in room temperature vulcanizable silicone elastomer compositions and term this silane an "in situ chain extender".
Although Toporcer and Clark describe chain extension as meaning that the molecular weight of the polydiorganosiloxane is effectively increased as observed from the properties of the cured silicone elastomer, they do not suggest making polydiorganosiloxanes. Likewise, Toporcer and Crossan suggest that their silanes are useful as chain extenders in silicone rubbers. Klebe does not suggest such chain extension but describes his silanes as useful to make rubbery siloxanes by hydrolysis.